MediumChemistryHigh School (9–10)GeneralThe Periodic Table › Development of the Periodic TableNumerical

The atomic masses of beryllium, magnesium and calcium are 9.0 u, 24.3 u and 40.1 u.

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

The atomic masses of beryllium, magnesium and calcium are $9.0\ \text{u}$ , $24.3\ \text{u}$ and $40.1\ \text{u}$ . Do they form a Dobereiner triad? Use the rule that the middle mass must be within $2\ \%$ of the average of the other two.

Need a reminder? The key ideaShow

Dobereiner: in a triad of three similar elements, the middle atomic mass is close to the average of the other two. Newlands: in order of atomic mass, every eighth element is like the first, which worked only up to calcium.

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

← All Problems

← Give two reasons why Newlands' law of octaves was not accepted for all of the elements.Mendeleev also predicted the oxide of eka-silicon. →

More onThe Periodic Table › Development of the Periodic Table

Discussion (0)

Loading…

The atomic masses of beryllium, magnesium and calcium are 9.0 u, 24.3 u and 40.1 u.

The worked solution

Discussion (0)

Want to go further in The Periodic Table › Development of the Periodic Table?